Tube push bench



Patented Jan. 11, 1938 PATENT OFFICE TUBE PUSH BENCH Kai-01 Korbuly, Csepel, Hungary, assignor to the firm Tube Industrial Participation Limited,

Breganzona-Lugano, land a corporation of Switzer- Application January 21, 1937, Serial No. 121,677

1 Germany June 29, 1936 This invention relates to push bench drawing apparatus for the manufacture of metal especially iron or steel tubes of the kind by which a heated somewhat thick cup-shaped hollow billet through-passes between rolls which passes decrease successively in cross-sectional area in a forward direction and which rolls are not driven, whereby the billet is reduced in thickness and spread out lengthwise along the mandrel until the billet is brought to the form of a tube of the required thickness and length.

In the operation of push bench apparatus in which ring dies are employed instead of through passes between rolls, if the resulting tube is to be at least ten times the length of the billet treated and the drawing is to be effected in one operation, the ring bed must be of a length to permit the spacing of the dies at such distances that the tube being drawn engages at most four, and in exceptional cases perhaps five dies simultaneously, when the head end of the tube enters the last orsmallest die, while in the major part of the ring bed it is acted on only by two or three dies simul the metal during the lengthening of the billet to more than ten times its original length a total number of dies exceeding 20 must be employed. The partly formed tube on entering the last or smallest die will thus be acted on simultaneously by less than one fourth, and generally by less than one fifth, of the total number of dies which are distributed along a shorter distance than the last quarter of the total length of the ring die bed, which has to be more than twice the length of the tube produced. The long stroke required not only results in slower working, but in conjunction with the cooling effect of the mandrel would cause the metal to cool so quickly that difiiculty would be experienced in drawing the tube were it not for the heating efiect produced by the friction between the dies and the tube. This, however, means that considerable power is required to push the tube through the dies.

n is an object of the present invention to provide apparatus of the kind described by which these disadvantages are overcome.

According to the present invention in push bench drawing apparatus of the kind described the number of roll passes is greater than the figure indicating the relation between the length of tended to stretch the billet b shown by dotted the drawn tube and the original length of the billet, and said passes are disposed at such distances apart that the partiallyformed tube when it enters the last and smallest pass extends over carried on an end of a mandrel is pushed through.

neously. In order to avoid a rupture of 2 Claims. (01. -12) at least the last third part of the total length of the whole series of passes and is acted on at one time by not less than one third of the total number of passes.

Preferably the passes are disposed at such distances apart that the partially formed tube when it enters the smallest roll pass .extends at least over the second half of the total length of the whole series ofpasses and is worked on simultaneously by not less than half of the total number of passes. The total length of the series of passes may be even less than the final length of the drawn tube, whereby the length of stroke required for the push bench can be less than twice the length of the tube to be produced.

The trough diameter of the rolls of a pass, that is, the diameter of the rolls measured at the bottom of the circumferential groove is, preferably, in the first or largest pass such that it does not exceed the pass diameter by more than 20%, while the trough diameter of the rolls of any other pass is smaller than the trough diameter of the rolls of the largest pass. The trough diameters of the rolls in a pass must be so chosen as to have a relation to the pass diameter of the respective pass such that the ratio of thetrough diameter to the pass diameter in the several passes decreases gradually from the last passtowards the first pass.

One form of push bench drawing apparatus according to the present invention will now be described by way of example and with reference to the accompanying partly diagrammatic drawing wherein:-

Fig. 1 is a diagrammatic elevation of the push bench,

Fig. 2 shows to a larger scale and diagrammatically the partly formed tube at the point at which it enters the smallest roll pass and Fig. 3 shows-a front elevation of a roll pass having three rolls arranged at Referring first to Fig. 3 r are the rolls which are loosely journalled in a carrier or housing s. The rolls are arranged at 120 and form a pass of whichD is the pass diameter. d is the trough diameter or diameter of the rolls measured at the bottom of the groove 9. While the pass illustrated in Fig. 3 has three rolls it will be understood that according to requirements two rolls or more than three rolls may be employed.

Referring now to Fig 1 the push bench is infor example seventeen passes a1arz, are ar- 55 dot and dash line at the left hand end of the figure. The trough diameter d of the rolls of the smallest and last pass a" is, for example 1.3 times the pass diameter D of this pass, while the trough diameter d of the first and largest pass a is equal to the pass diameter of this said first pass. Hence, the ratio decreases gradually from the smallest and last pass a" towards the first and largest pass a The partially drawn tube w is indicated in Fig. 1 in full lines and it is at the stage when it is entering the smallest pass a". At this stage the partially formed tube extends over a length of 6.7 L, that is to say over a length which is larger than half of the total length 11L of the pass bed. At this stage also the tube is acted on simultaneously by eleven passes a -a" at one time. Fig. 2 shows the partly drawn tube at this stage and to a larger scale. The total number of passes in the push bench illustrated being seventeen the number of passes acting on the tube at this stage, namely, eleven, is substantially greater than one third of the total number of passes and is even greater than half the total number of passes.

The total number of passes (l -a" in the apparatus illustrated diagrammatically in Fig. 1 extends over a length which is about equal to 11L, that is to say, the total length of the passes is less than the length of the tube produced which is indicated in Fig. 1 as being 13L.

What I claim is:

1. A push bench drawing apparatus for producing a tube from a hollow billet, the length of which tube is at least ten times the length of the hollow billet, comprising a mandrel and roll passes, in which the rolls are idle, disposed in front of the mandrel, the number of said passes being greater than the figure indicating the relation between the length of the drawn tube and the original length of billet, said passes being disposed at such distances apart and decreasing successively in cross-sectional area in forward direction in such stages that the tube on entering the last and smallest pass reaches a length which extends at least to the last third of the total length of the whole series of passes and is acted on simultaneously by not less than one-third of the total number of passes.

2. A push bench drawing apparatus for producing a tube from a hollow billet, the length of which tube is at least ten times the length of the hollow billet, comprising a mandrel and roll passes, in which the rolls are idle, disposed in front of the mandrel, the number of said passes being greater than the figure indicating the relation between the length of the drawn tube and the original length of billet, said passes being disposed at such distances apart and decreasing successively in cross-sectional area in forward direction in such stages that the tube on entering the last and smallest pass reaches a length which extends at least to the second half of the total length of the whole series of passes and is acted on simultaneously by not less than one-half of the total number of passes.

KARoLY KORBULY. 

